The invention relates to a method for operating an internal combustion engine in which a glow ignition state (pre-ignition state) of the internal combustion engine is determined. The internal combustion engine comprises a cylinder in which a combustion chamber is provided that is delimited by a reciprocating piston guided in the cylinder wherein the piston is connected by a connecting rod to a crankshaft and wherein the internal combustion engine has a device for supplying fuel and a device for igniting the fuel/air mixture in the combustion chamber.
U.S. Pat. No. 5,526,788 discloses a method for determining a glow ignition state (pre-ignition state) of the internal combustion engine. In this method, the spark plug is utilized for determining the pre-ignition state. For this purpose, the current supply to the spark plug is measured and evaluated. This requires a comparatively complex electronic evaluation circuit.